Method and apparatus for removing naphthalene from coke oven gas



J1me 1955 P. J. WILSON, JR

METHOD AND APPARATUS FOR REMOVING NAPHTHALENE FROM COKE OVEN GAS Flled April 17 1952 lowenior: PH/L ,/P J Mafia/M2,

bXQ WK United States Patent O METHOD AND APPARATUS FOR REMOVING NAPHTHALENE FROM COKE OVEN GAS Philip J. Wilson, .lr., Sewickley, Pa., assignor to United States Steel Corporation, a corporation of New Jersey Application April 17, 1952, Serial No. 282,919

9 Claims. (Cl. 183-2) This invention relates to a method and apparatus for removing naphthalene from coke oven gas. Naphthalene is ordinarily removed from coke oven gas because it is a useful chemical and also because if allowed to remain in the gas it will be condensed from the gas as crystals at points in the gas main where the temperature of the gas is reduced. Accumulation of the crystals thus formed would cause stoppages in the gas distribution system. In some instances naphthalene and light oils have been removed from the gas after both the tar and ammonia have been removed. This process is unsatisfactory because naphthalene is precipitated in-the form of crystals. in the final cooler to give a gas saturated with naphthalene, thus often causing accumulations of naphthalenein the pipes and apparatus; the precipitated naphthalene also contaminates the cooling water and air, and the quality of any naphthalene recovered is relatively poor. In some instances naphthalene is removed prior to this point but in these processes the cost of removal and recovery is expensive.

.It is therefore an object of my invention to provide a method of removing naphthalene from coke oven gas which is inexpensive and which will not cause interference to the flow of gas due to the accumulation of naphthalene deposits in the mains and other apparatus.

Another object will be to provide apparatus suitable for carrying out the method of my invention.

These and other objects will be more apparent after referring to the following specification and attached drawing in which the single figure is a schematic layout of the apparatus of my invention.

Referring more particularly to the drawing, reference numeral 2 indicates a primary cooler. Gas from the coke oven is delivered to the bottom of the primary cooler through a conduit 4. The cooled gas passes from the top of the cooler 2 through a conduit 6 to the bottom of naphthalene scrubber 8. Wash oil is delivered to the top of the naphthalene scrubber 8 through a conduit 10. A solution of wash oil and naphthalene with some light oil therein is delivered from the bottom of the scrubber 8 through a conduit 12 and preheater 14 into the top of a light oil and naphthalene stripping still 16. The stripped gas passes from the top of the scrubber 8 through conduit'18 and is then handled in the conventional manner through the exhauster 20, reheater 22, saturator 24, acid separator 26 and final cooler 28. From the final cooler 28 the gas passes into the bottom of a light oil scrubber 30. Wash oil is delivered to the top of the scrubber 30 through a conduit 32. A pump 34 delivers light oil and wash oil through conduit 36, heat exchanger 38 and preheater 40 into the still 16 at a point 42 intermediate the height of the still. Steam is delivered into the bottom of the still through conduit 44. Wash oil from the bottom of the still 16 is deliveredby means of a pump 46 through the heat exchanger 38 and cooler 48 into a conduit 50 which is connected to conduits and 32. Valves 52 and 54 are provided in the conduits 10 and 32, respectively. An outlet 56 for wash oil is provided in the still 16 at approximately the level of the point 42. While the conduit .56 is shown at the same level as point 42 where the light oil and wash oil is introduced it will be understood that the conduit 56 may be located either somewhat above or below this point. The outlet 56 is connected to a cooler 58 which is connected to the conduit 10 through a conduit 60 having a ice valve 62 therein. Light oil and naphthalene pass out of the top of the still 16 through a conduit 64 into a rectifier 66 where wash oil is removed and returned through a conduit 68 to the top of the still 16. The light oil and naphthalene then pass through conduit 70 to a condenser 72 and hence to a fractionating still 74 where the light oil and naphthalene are separated in the usual manner.

The operation of the device is as follows: The concentration of the naphthalene in the coke oven gas is reduced by scrubber 8 to a point which is low enough to prevent formation of naphthalene deposits when the gas is cooled at later stages of treatment and distribution. A quantity of steam equal to that normally used for stripping light oil alone is delivered into the bottom of the still 16 and passes upwardly therethrough stripping the light oil from the wash oil as it ascends through the bubble plates. When the steam leaves the top of the light oil section it immediately enters the base of the naphthalene stripping section which is above point 42. Here it meets the naphthalene wash oil solution from the scrubber 8 and picks up the naphthalene contained in the oil. The light oil which has previously been picked up by the steam also acts as a stripping medium for the naphthalene. It will be understood that the naphthalene will have been substantially removed from the wash oil at point 42 so that troubles due to naphthalene will not occur when the Wash oil is again used for scrubbing the coke oven gas. All of the wash oil may be removed from the bottom of the still 16 and delivered through conduit 50 to the top of the naphthalene scrubber 8 and the light oil scrubber 30. The valves 52 and 54 control the flow of the wash oil to the two scrubbers. Another method of operation is to withdraw wash oil from the base of the naphthalene stripping section through outlet 56, cool it and return it through the conduit 60 to the naphthalene scrubber 8. This wash oil will carry some light oil but the light oil content will not affect the absorption of the naphthalene and any light oil returned to the gas in the naphthalene scrubber will be recovered in the light oil scrubber 30. The remaining wash oil will then be delivered from the bottom of the still 16 into thetop of the light oil scrubber 30. This latter method of operation requires the closing of valve 52 and the opening of valve 62.

In general the volumeof wash oil used in the naphthalene scrubber will be a fraction of that used for removing light oil from the gas. The proportion may be 0.7 gallon per 1000 cu. ft. of gas to the naphthalene scrubber and 10 to 15 gallons per 1000 cu. ft. of ga through the light oil scrubber.

- While two embodiments of my invention have been shown and described it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

1. Apparatus for removing naphthalene from coke oven gas comprising a primary cooler for said gas, a naphthalene scrubber, a conduit connecting said primary cooler to the bottom of said naphthalene scrubber, a still, means for introducing wash oil into the top of said naphthalene scrubber, means for delivering naphthalene and wash oil from the bottom of said naphthalene scrubber to the top of said still, a light oil scrubber, means for delivering the coke oven gas from the top of said naphthalene scrubber to the bottom of said light oil still, and means for delivering wash oil from said still to the top of said scrubbers.

2. Apparatus for removing naphthalene from coke oven gas comprising a primary cooler for said gas, a napthalene scrubber, a conduit connecting said primary cooler to the bottom of said naphthalene scrubber, a still, means for introducing Wash oil into the top of said naphthalene scrubber, means for delivering naphthalene and wash oil from the bottom of said naphthalene scrubber to the top of said still, a light scrubber, means for delivering the coke oven gas from the top or" said naphthalene scrubber to the bottom of said light oil scrubber, said last named means including a reheater, saturator and final cooler, means for introducing wash oil into the top of said light oil scrubber, means for delivering light oil and wash oil from the bottom of said light oil scrubber to said still at a point intermediate its height, means for introducing steam into the bottom of said still, means for removing light oil and naphthalene from the top of said still, and means for delivering wash oil from said still to the top of said scrubbers.

3. Apparatus for removing naphthalene from coke oven gas comprising a primary cooler for said gas, a naphthalene scrubber, a conduit connecting said primary cooler to the bottom of said naphthalene scrubber, a still, means for introducing wash oil into the top of said naphthalene scrubber, means for delivering naphthalene and wash oil from the bottom of said naphthalene scrubber to the top of said still, a light oil scrubber, means for delivering the coke oven gas from the top of said naphthalene scrubber to the bottom of said light oil scrubber. means for introducing wash oil into the top of said light oil scrubber, means for delivering light oil and wash oil from the bottom of said light oil scrubber to said still at a point intermediate its height, means for introducing steam into the bottom of said still, means for removing light oil and naphthalene from the top of said still, means for delivering wash oil from the bottom of said still to the top of said light oil scrubber, and means for delivering Wash oil from the still at a point adjacent the light oil and wash oil inlet to the top of said naphthalene scrubber.

4. Apparatus for removing naphthalene from coke oven gas comprising a primary cooler for said gas, a

naphthalene scrubber, a conduit connecting said primary cooler to the bottom of said naphthalene scrubber, a

still, means for introducing wash oil into the top of said naphthalene scrubber, means for delivering naphthalene and wash oil from the bottom of said naphthalene scrubber to the top of said still, a light oil scrubber, means for thalene scrubber to the bottom of said light oil scrubber, means for introducing Wash oil into the top of said light oil scrubber, means for delivering light oil and wash oil from the bottom of said light oil scrubber to said still at a point intermediate its height, means for introducing steam into the bottom of said still, means for removing light oil and naphthalene from the top of said still, and means for delivering wash oil from the bottom of said still to the top of said scrubbers.

5. Apparatus for removing naphthalene from coke oven gas comprising a primary cooler for said gas, a naphthalene scrubber, a conduit connecting said primary cooler to the bottom of said naphthalene scrubber, a still, means for introducing wash oil into the top of said naphthalene scrubber, means for delivering naphthalene and wash oil from the bottom of said naphthalene scrubber to the top of said still, a light oil scrubber, means for delivering the coke oven gas from the top of said naphthalene schubber to the bottom of said light oil scrubber, said last named means including a reheater, saturator and final cooler, means for introducing wash oil into the top of said light oil scrubber, means for delivering light oil and wash oil from the bottom of said light oil scrubber to said still at a point intermediate its height, means for introducing steam into the bottom of :Z; delivering the coke oven gas from the top of said naphsaid still, means for removing light oil and naphthalene from the top of said still, means for delivering wash oil from the bottom of said still to the top of said light oil scrubber, and means for delivering wash oil from the still at a point adjacent the light oil and wash oil inlet to the top of said naphthalene scrubber.

6. Apparatus for removing naphthalene from coke oven gas comprising a primary cooler for said gas, a naphthalene scrubber, a conduit connecting said primary cooler to the bottom of said naphthalene scrubber, a still, means for introducing wash oil into the top of said naphthalene scrubber, means for delivering naphthalene and wash oil from the bottom of said naphthalene scrubber to the top of said still, a light oil scrubber, means for delivering the coke oven gas from the top of said naphthalene scrubber to the bottom of said light oil scrubber, said last named means including a reheater, saturator and final cooler, means for introducing wash oil into the top of said light oil scrubber, means for delivering light oil and wash oil from the bottom of said light oil scrubber to said still at a point intermediate its height, means for introducing steam into the bottom of said still, means for removing light oil and naphthalene from the top of said still, and means for delivering wash oil from the bottom of said still to the top of said scrubbers.

7. The method of removing naphthalene from coke oven gas comprising passing the coke oven gas through a naphthalene scrubber after the gas passes through the primary cooler, passing the stripped gas through a second cooler to a light oil scrubber, delivering the naphthalene and wash oil from the naphthalene scrubber to the top of a light oil and naphthalene stripping still, delivering the light oil and wash oil from the light oil scrubber to the still at a point intermediate its height, delivering steam into the bottom of the still and passing it up through the naphthalene, light oil and wash oil to remove the light oil and naphthalene, and delivering Wash oil from the still to the top of said scrubbers.

8. The method of removing naphthalene from coke oven gas comprising passing the coke oven gas through a naphthalene scrubber after the gas passes through the primary cooler, passing the stripped gas through a second cooler to a light oil scrubber, delivering the naphthalene and wash oil from the naphthalene scrubber to the top of a light oil and naphthalene stripping still, delivering the light oil and wash oil from the light oil scrubber to the still at a point intermediate its height, delivering steam into the bottom of the still and passing it up through the naphthalene, light oil and wash oil to remove the light oil and naphthalene, delivering wash oil from the bottom of said still to the top of said light oil scrubber, and delivering wash oil from the still at a point adjacent the light oil and wash oil inlet to the top of said naphthalene scrubber.

9. The method of removing naphthalene from coke oven gas comprising passing the coke oven gas through a naphthalene scrubber after the gas passes through the primary cooler, passing the stripped gas through a second cooler to a light oil scrubber, delivering the naplr thalene and wash oil from the naphthalene scrubber to the top of a light oil and naphthalene stripping still, delivering the light oil and wash oil from the light oil scrubber to the still at a point intermediate its height, delivering steam into the bottom of the still and passing it up through the naphthalene, light oil and wash oil to remove the light oil and naphthalene, and delivering wash oil from the bottom of the still to the top of said scrub- Reynolds Aug. 18, 1953 

7. THE METHOD OF REMOVING NAPHTHALENE FROM COKE OVEN GAS COMPRISING PASSING THE COKE OVEN GAS THROUGH A NAPHTHALENE SCRUBBER AFTER THE GAS PASSES THROUGH THE PRIMARY COOLER, PASSING THE STRIPPED GAS THROUGH A SECOND COOLER TO A LIGHT OIL SCRUBBER, DELIVERING THE NAPHTHALENE AND WASH OIL FROM THE NAPHTHALENE SCRUBBER TO THE TOP OF A LIGHT OIL AND WASH OIL FROM THE LIGHT OIL LIVERING THE LIGHT OIL AND WASH OIL FROM THE LIGHT OIL SCRUBBER TO THE STILL AT A POINT INTERMEDIATE ITS HEIGHT, DELIVERING STEAM INTO THE BOTTOM OF THE STILL AND PASSING IT UP THROUGH THE NAPHTHALENE, LIGHT OIL AND WASH OIL TO REMOVE THE LIGHT OIL AND NAPHTHALENE, AND DELIVERING WASH OIL FROM THE STILL TO THE TOP OF SAID SCRUBBERS. 